Historically in the United States authorities such as city, state, or federal police authorities, may legally engage in electronic surveillance (frequently referred to in the vernacular as wire-tapping), when duly authorized to perform such an activity by a cognizant judicial authority. Such surveillance may include delivery of call related signaling data to the authority or delivery of both signaling data and actual content of communications to and from the subject of the surveillance.
In earlier times, when public telephone service was virtually all analog, the procedures were relatively simple. Assuming surveillance of a residence connected to the telephone network by a local loop consisting of a pair of copper wires, the usual practice was to locate a convenient cross connect and bridge on to the two wire analog circuit. The entity conducting the surveillance then engaged the serving telephone network operator or company to provide a circuit from that location to the law enforcement location. The law enforcement organization could then monitor the conversations, generally referred to as content, as well as the call set up and related signaling.
Statistically approximately 90 percent of the authorized surveillance in the United States does not cover content but only signaling data. Signaling data surveillance is performed through a Pen register tap. A pen register is a dialed number recorder. The register includes a dial pulse detector and/or a dual tone multi-frequency decoder, connected to the line serving the subject party. A memory or recording device captures detected dialing information. However, this register accumulates only dialing information and only that for the connected line.
With the widespread use of digital communication and control signaling, the simplicity and ease of the prior surveillance procedures has largely disappeared. As a result, law enforcement agencies, and cooperating Public Switched Telephone Network (PSTN) carriers, are forced to cope with a considerably more complex and costly substitute set of procedures. Partially in response to this situation Congress passed Public Law 103-414, the Communications Assistance for Law Enforcement Act (CALEA). The Telecommunications Industry Association (TIA), accredited by the American National Standards Institute (ANSI), was selected by the telecommunications industry to promulgate the industry's CALEA standard. The TIA promptly initiated a standards program. Initial disagreements within industry were resolved, and TR45 Lawfully Authorized Electronic Surveillance SP-3580, Baseline Revision 10 was produced. The baseline requirements specified in this standard have become known as the "safe harbor" standards, pending resolution of still outstanding differences with respect to certain preferences of the Federal Bureau of Investigation (FBI).
The CALEA specifications include a requirement that the subject under surveillance continue to receive all subscribed enhanced, CLASS, and other services. The surveillance must be completely transparent, to the subject and to other parties communicating with the subject. The central office switches currently in use in the public switched telephone networks were not designed with CALEA functions in mind. As a result it is not surprising that many existing switches can not be easily adapted to meet major CALEA requirements.
The basic surveillance problem has undergone continued evolution as telecommunications technology has advanced and provided the public with an ever-increasing variety of services. Illustrative of such services, which create added complexity for effective telephone surveillance, is call forwarding or redirection, call conferencing, call waiting, bill to third party calling, etc. Another example is central office based speed dialing.
Since the proposed CALEA requirements are worded in terms of service, i.e., monitoring the telephone service (signaling and speech) of the subject, and anything that can be accomplished with the service, significant problems are presented by such enhanced network services. This becomes particularly acute when coupled with a desire that the surveillance capability should be almost universally applicable to all telephone central offices, including end offices that rely on legacy switches.
Of particular note, the new CALEA standards impose a significantly increased requirement for delivery of signaling data regarding communications associated with the subject of the surveillance. The call associated information must include the signaling data relating to the subject party as well as any other parties to the call. The information must also include a variety of other data, for example relating to called party and calling party identities, relating to call redirection, relating to interexchange carrier identity, and the like. The law requires delivery of call related signaling data for subjects under content surveillance, although the signaling data may be delivered separately from the content delivery. Also, many surveilance operations will continue to involve delivery of only the call associated signaling data.
It has been suggested that the carriers implement the CALEA standard, both for content and call data delivery, by deploying specialized surveillance equipment in offices of the carriers' networks. Deployment of such equipment or other forms of office upgrades in a large number of offices, to satisfy the surveillance requirements, will require a large capital investment. Processing of calls through such specialized equipment raises questions of whether or not the surveillance might be detectable by the target. It has been suggested that, for subjects served from offices not complying with CALEA, the subjects calls could be routed and processed for surveillance through an office having full CALEA compliant capabilities. Many approaches to such routing would be detectable by the subject or parties in communication with the subject.
As described for example in parent application Ser. No. 09/112,155, Applicants have developed solutions, which make the services entirely transparent while processing calls through a CLEA compliant office. The routing to the CALEA compliant office is effective in some situations, particularly where content delivery is required. However, even this approach imposes some costs, for increased interoffice routing and/or for specialized routing control from a service control point or the line. Also, if CALEA compliant equipment in an office is necessary for every surveillance, even for data only surveillance, it forces the carrier to upgrade more offices to insure capacity to handle all expected surveillances.
A need still exists for a cost-effective mechanism to provide the desired level of surveillance, in the modern telecommunications world, while maintaining secrecy of the surveillance, particularly with respect to signaling data delivery.
The telecommunication networks today utilize a wide range of signaling messages and data recording systems, to control set-up and tear down of calls, to record billing information, and the like. Deployment of new equipment to record signaling data for surveillance purposes adds another layer of expense and complexity to operation and maintenance of the telecommunication switching offices.
A specific need therefore exists for a cost-effective technique for accumulating the call signaling data for surveillance purposes. To meet this specific need, any solution should minimize the requirements for installation of new hardware, particularly hardware at the individual office level. Any new hardware for the surveillance should be as centralized as possible, yet provide the requisite data for subjects served through many local offices. Also, it is desired that the surveillance technique impose no new processing steps, during routing of the call, to insure transparency to the subjects.
It is accordingly an object of the present invention to provide a relatively straightforward and cost-effective solution to the foregoing problems of signaling data delivery for lawfully authorized electronic surveillance.